This invention relates generally to adhesive attachment assemblies or fixtures and related methods for securing an attachment component or the like to a supporting surface or substrate. More specifically, this invention relates to improvements in such adhesive attachment assemblies or fixtures, of the general type shown and described in U.S. Pat. Nos. 4,302,492; 4,338,151; 4,390,576; 4,668,546; 4,778,702; 4,822,656; 4,842,912; 5,013,391; 5,704,747; 5,603,472; 6,727,466; and 6,773,780, and particularly with respect to providing a substrate ground path for electrically grounding the attachment component and/or a selected structure mounted thereto.
In many instances, it is necessary or desirable to mount an attachment component or element such as a patch, threaded screw, or other structure onto a supporting substrate. For example, it may necessary to apply a thin patch to the skin of an aircraft or to the hull of a boat to repair a hole therein. Alternately, it may be desirable to mount a threaded element, such as a threaded stud or nut, or other device onto a substrate without requiring a hole to be made in the substrate, and wherein the threaded element or the like is adapted for subsequent mounting of a selected structure such as a cable tie for supporting one or more conductive cables, or an electrical junction box, or the like. In many such cases, it is necessary for the attachment component to be located on the substrate with relatively high precision and further that a positive force be applied for urging or pressing the attachment component against the substrate for at least some minimum time period to allow, for example, curing of an adhesive bonding agent such as a curable epoxy or the like to achieve a substantially optimized and secure bond with the substrate.
Exemplary adhesive attachment assemblies and related attachment fixtures designed for quick and easy mounting of an attachment component on a substrate, while achieving a high bond strength, are shown and described in U.S. Pat. Nos. 4,302,492; 4,338,151; 4,390,576; 4,668,546; 4,778,702; 4,822,656; 4,842,912; 5,013,391; 5,704,747; 5,603,472; 6,727,466; and 6,773,780, all of which are incorporated by reference herein. In such products, an attachment component is adhesively mounted directly onto the substrate, or otherwise carried by a support fixture that is adhesively mounted onto the substrate. In each configuration, the attachment component or the associated support fixture is inherently spaced from the surface of the substrate by a relatively thin film of adhesive bonding agent, wherein this bonding agent typically exhibits relatively nonconductive or dielectric properties. In other words, the adhesive bonding agent effectively insulates the attachment component or support fixture from electrical communication with the substrate.
In some applications, it is necessary or desirable to mount the attachment component and/or the associated support fixture in electrical conductive contact with the substrate. For example, some structures such as an electrical junction box or the like adapted for mounting onto the attachment component are designed to be electrically connected to a suitable ground point, such as by connection to the substrate which may be formed from or otherwise incorporate a conductive material. However, as noted above, the adhesive bonding agent effectively insulates the attachment component or related support fixture from the substrate. Accordingly, in the past when a grounded connection has been required, a metal attachment component has typically been welded to the substrate in lieu of using an adhesive bonded interface. Such welded attachments inherently require specialized equipment and trained personnel, and further require that the attachment component and substrate be constructed from weld-compatible metal materials. For some materials such as aluminum and composites of the type used widely in the aerospace industry, welding steps cannot be employed.
One potential solution to this problem comprises the use of an electrically conductive adhesive bonding agent formed by loading an otherwise substantially dielectric adhesive bonding agent with conductive particles, so that the attachment component and/or related support fixture can be adhesively mounted in electrically conductive relation to the substrate. However, conductive particle inclusions adversely and undesirably weaken the bond strength of the adhesive material. In addition, the current-carrying capacity of the conductive particle inclusions is insufficient for many applications, and further exhibits a tendency to deteriorate over time.
There exists, therefore, a significant need for improvements in and to adhesive attachment assemblies for adhesively mounting an attachment component or related support fixture onto a substrate, wherein the attachment component and/or support fixture and/or a selected structure mounted subsequently mounted thereto is electrically grounded to the substrate in a safe and effective manner. The present invention fulfills these needs and provides further related advantages.